There is no postwork to the figures in the promotional ads.
UW (underwater) texture is an extra texture to add realism. It can be assigned to either of the ground planes, and all the morphs work on it. Colm made the ground that way so that it would be compatible with all the microcosm textures. It just gives a wet, "pebble" effect to the bottom and adds another dimension to the reality. I usually keep it flat, or use a not-too-bumpy morph on it, so that it stays "Underwater". The entire texture is meant to stay underwater or give a "slick bank" effect if used above the water. It's really not necessary to the far-away scene, but comes in very handy for close-up shots when the bottom of the water plane shows in the image. It's also cool for shots looking down into the water. I've been experimenting with that. You can get a cool "floating" or even a "dead-in-the-water" effect by placing your character just under the water plane with an underwater plane below the character....the Ophelia Effect.
Crocodile is by “noggin” and is from DAZ.